(1) Field of the Invention
The invention relates to a method of diagnosing nutrition of crop by obtaining crop information represented by nitrogen content, etc. of the crop from reflection light of the crop growing in a field.
(2) Description of the Related Art
A first conventional method for obtaining crop information such as a nitrogen content rate of a crop, a leaf color value, a nitrogen absorption amount, a plant height, a dry matter weight, etc., is one in which the amount of reflection light from the reference plate and that from the crop in the field is obtained by image-taking, by a light receiving means such as a digital camera, the reference plate which is coated with barium sulfate, etc. and the unit field (or a part of it) in which the crop grows, the reflectivity of the crop is obtained from the amount of the light reflected from the reference plate and the crop, and the nitrogen content rate (amount of nitrogen absorption, a value of leaf color, a plant height, a dry matter weight) is obtained from the reflectivity obtained and the relation formula predetermined for obtaining the nitrogen content rate (amount of nitrogen absorption, a value of leaf color, a plant height, a dry matter weight) from the reflectivity, and the growth diagnosis has been conducted by comparing with a standard nitrogen content rate of that time period based on the number of growth days versus the nitrogen amount curve. However, the amount of reflection light of the crop to be obtained from the field is subject to change by weather. Also, even when the weather is compensated by the reference plate, it is necessary that each of the measuring direction, wind, and planting density be in the same condition as that applied when the predetermined relation formula was prepared for obtaining the nitrogen content rate from the reflectivity. When the condition is different, the compensation is necessary accordingly, so that it cannot be said that all has been compensated only by obtaining the reflectivity by the reference plate as reference. Actually, the measurement has been conducted under the limitation by the solar height, measuring direction, planting density or kind.
As for a second conventional method for obtaining crop information, there is an apparatus in which the light with a wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop, for example, the light ranging from a visible light region to a near infrared region is irradiated on a leaf blade of the crop and, based on the amount of the received light obtained with respect to the light with the wavelength having relation to the crop information and on the nitrogen amount related formula predetermined for calculating from the amount of light received, for example, a leaf blade nitrogen content, the leaf blade nitrogen content is measured. This apparatus is used to measure a number of the leaf blades of the crop in the field and has enabled to obtain the leaf blade nitrogen content with a high precision. However, in order to grasp the crop information accurately for the overall field, a minute measurement to extend to the overall field was indispensable, which is complicated and troublesome.
The first conventional method described above is one in which, although the measurement is simple, the crop information to be obtained from the field is influenced by factors such as a measuring location and a planting density and, because of constraint in the measuring time and location, the method cannot be regarded as accurate. The second method, having no restraint in the measurement and having a high precision, is more advantageous than the first method. However, the problems in the second method are that the measurement has to be made for each leaf blade, thus requiring a large number of points to be measured and a long time accordingly.
An object of the present invention is that, when obtaining the crop information by measuring the amount of reflection light, the compensation can be made so that no large error occurs caused by the measuring locations and the planting densities, and a method of diagnosing nutrition of the crop provided is simple and easy in the measurement of the crop information and enhances the measurement precision.
A first method of the invention is a method of diagnosis for crop in a field in which, from crop in a fixed area in a crop field under exposure to the natural light, reflectivity of light with a wavelength having relation to crop information which increases or decreases depending on growth of the crop is measured; crop information of a predetermined area from said reflectivity and a first crop related formula predetermined from reflectivity for obtaining crop information is obtained and stored as first crop information; an amount of at least either of transmission light or reflection light with a wavelength having relation to the crop information which increases or decreases depending on growth of the crop is measured; crop information from said amount of light and a second crop related formula predetermined from an amount of light for obtaining crop information is obtained and stored as second crop information; a difference between said first crop information and said second crop information is obtained; the first crop information is obtained from the unknown crop of a predetermined area in the same field; the first crop information is compensated based on said difference; and the nutritious diagnosis of the crop in the field is made based on said first compensated crop information.
The obtaining of the first crop related formula by obtaining the reflectivity obtained from the amount of reflection light of the crop and the amount of reflection light for obtaining the first crop information in advance has been subject of research and is conventional, and also the obtaining of the second crop related formula for obtaining the second crop information determined by obtaining the reflectivity by irradiating light on leaves has also been subject of research and is conventional. Therefore, such information can readily be obtained. According to the invention, and the two useful means mentioned above are effectively combined, the difference between the first crop information and the second crop information respectively obtained from the two means is calculated. By using this difference for compensating the first crop information, it is possible to compensate not only the errors caused by weather changes (weather, time, solar position) but also the errors caused by changes in cultivation factors (measuring direction, planting density) which have heretofore been considered difficult to be compensated. This method is especially suited for conducting nutrition diagnosis at a plurality of spots in the same field because the compensation can be performed simply and easily.
Where the difference between the first crop information and the second crop information decided as above is stored, only by obtaining the first crop information from the unknown crop in the fixed area in the field from which the first crop information has been obtained, it is possible to compensate the first crop information by the first crop information and the above difference. This method enables the easy compensation of the errors caused by the planting density and the measuring direction, and the method may be embodied in an apparatus with the compensation value being provided. Such apparatus can be readily used for crop nutrition diagnosis.
A second invention relates to a method of diagnosis for crop in which, from the crop in the fixed area in a field under exposure to the natural light, the reflectivity of light which has wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop is measured; crop information for each division is calculated based on the reflectivity for each division of a plurality of divisions and the first crop related formula predetermined for obtaining the crop information from the reflectivity, and such information is made the first crop information and stored; the crop information of at least two divisions from the first crop information stored for each division is selected; light is irradiated on the leaf blade falling within the two divisions of the field; at least either of the transmission light or reflection light which has wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop is measured; crop information of the two divisions is calculated from said amount of light and the crop related formula predetermined for obtaining the crop information from the amount of light and such information is made the second crop information and stored; a compensation conversion formula for compensating the first crop information based on the second crop information is determined; the first crop information is compensated for each division by the compensation conversion formula and is made the third crop information; and the nutritious diagnosis of the crop in the plant field is made by the resulting third crop information.
For conducting a more strict compensation than in the first crop nutrition diagnosing method, the second crop nutrition diagnosing method is applied. That is, after the crop information is obtained and divided into a plurality of divisions, at least two points of data from within the plurality of divisions are selected, and the second crop information is obtained directly from the crop leaves in the same field as the field from which the two points of data are selected. Thus, from the two points of data of the first and the second crop information, the correlation thereof is determined and the compensation related formula is defined and, based on this formula, all the values in the plurality of divisions are compensated. In obtaining the compensation related formula, the plurality of crop information can be obtained from the fixed extent of area and, further, from the compensation related formula, the first crop information can be compensated for a large extent of area.
In the first and the second nutrition diagnosing methods explained above and the crop diagnosis to which such methods are applied, the first crop information may be obtained for each unit crop field, or may be obtained for each unit area which is arbitrary determined and which is smaller than the unit crop field. The unit crop field here refers to one field divided by what is normally called xe2x80x9cfurrowxe2x80x9d.
A third invention relates to a method of diagnosis for crop in which, from the crop in each division of a plurality of divisions in a field exposed to the natural light, the reflectivity of light which has wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop is measured; the crop information for each division is calculated from the reflectivity and the first crop related formula predetermined for obtaining the crop information from the reflectivity and such information is made the first crop information and stored; the crop information of at least two divisions from the first crop information stored for each division is selected; light is irradiated on the leaf blade falling within the two divisions of the field; at least either of the transmission light or reflection light which has wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop is measured; crop information of the two divisions is calculated from said amount of light and the crop related formula predetermined for obtaining the crop information from the amount of light and such information is made the second crop information and stored; a compensation conversion formula for compensating the first crop information based on the second crop information is determined; the first crop information is compensated for each division by the compensation conversion formula and is made the third crop information; and the nutritious diagnosis of the crop field is made by the resulting third crop information.
Unlike the above second crop diagnosing method, the third method obtains the information relating to the plurality of divisions individually. The data of at least two divisions are selected from among the plurality of divisions and, by obtaining the second crop information directly from the crop leaves in the same divisions as those of the data in the two divisions, the correlation between the first crop information and the second crop information is determined by the data of the two points and the compensation related formula is defined. Based on this formula, all the values of the plurality of divisions can be compensated. In obtaining the compensation related formula, the plurality of crop information can be obtained from a large extent of area and, further, from the compensation related formula, the first crop information can be compensated for a large extent of area.
As to the division in the third crop diagnosing method, the unit crop field may be formed of one division, the first crop information may be obtained from a plurality of unit crop fields, or the first crop information may be obtained in each division from a plurality of divisions set within the unit crop field.
In the second and third crop diagnosing methods described above, the first crop related formula and the compensation conversion formula are stored and the reflectivity from the crop leaves of unknown fields is measured whereby, based on the first crop related formula and the compensation conversion formula, the third crop information can be obtained. Where these items are stored in a memory section of a control means and are used for appropriate operation, the method can be realized as an apparatus which, not only realizes the diagnosing of the crop but also contributes in enhancing the precision in the measurement.
Concerning the second and the third crop diagnosing methods, the arbitrary two divisions to be selected from among the plurality of divisions may be divisions of the maximum value and the minimum value, respectively, from the first crop information. In this way, the straight line in the compensation conversion of the first crop information and the second crop information can be determined readily at the two points, high and low, without being affected by the remaining data.
There can be various crop information but, for purposes of diagnosing nutrition of the crop, the nitrogen content of leaves or the color values of leaves are considered the best. This is understandable from the fact that, in the crop, the nitrogen content in leaves is the factor which immediately shows the effectiveness of the fertilization or whether the fertilization is appropriate or not.
In the first through third crop diagnosing methods, in order to measure the reflectivity of the light which has wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop, the reflectivity of the crop is image-taken by the image-taking elements constituted by a plurality of image elements, the image elements having received the reflection light corresponding to the crop are selected, and the reflectivity is measured based on the light received data of the selected image element, thereby providing a method of diagnosing the crop by obtaining the first crop information. The reflection light obtained by an image-taking means such as a digital camera is influenced by the planting density or the dimension of the image-taken field, for example, whether the unit field is within the extent of 1 m2, so that the light image-taken of the crop as the reflection light is not necessarily the reflection light. That is, from the stand point of the unit image element, the reflection light from other than the crop, for example, the light reflected from the soil of the field may be included. Thus, only the image elements which relate to the reflectivity of the predetermined extent of area is selected and is used as the reflection light from the crop, and the first crop information is obtained based on such data of the received light.